1. Field of the Invention
The present invention relates to a cooling system for a diesel engine having a turbocharger which improves output at a low-speed section using a turbocharger, and improves combustion efficiency and quality of exhaust gas.
2. Description of Related Art
In general, it is known that a diesel engine consumes less fuel and has excellent efficiency in comparison with a gasoline engine. Typically, the diesel engine exhibits efficiency of about 40%, which results from a high compression ratio of the diesel engine.
The recent diesel engine additionally has a turbocharger, an intercooler, and the like in order to obtain higher output.
The diesel engine to which the turbocharger is applied as described above sucks and compresses exhaust gas or external air using a compressor of the turbocharger, and supplies supercharged air (high-temperature compressed air), which is generated by the turbocharger, to an engine side.
However, the air, which is rapidly compressed, absorbs heat from the turbocharger and heat that is generated during a compression process, such that density of the air is decreased, and as a result, charging efficiency in a combustion chamber of the engine deteriorates.
Therefore, high density may be obtained by cooling the supercharged air using the intercooler, and as a result, a larger amount of air may be sucked in the combustion chamber of the engine, thereby obtaining high output.
Moreover, in order to reduce emissions of nitrogen oxide (NOx), which is one of the air pollutants, an exhaust gas recirculation (EGR) device is mounted in the diesel engine.
The nitrogen oxide is noxious gas that is generated when oxygen and nitrogen are combined under a high-pressure and high-temperature condition, and in order to suppress the nitrogen oxide, the exhaust gas recirculation (EGR) device supplies a part of exhaust gas, which is discharged into the atmosphere, to an intake system to lower a maximum combustion temperature, and reduces oxygen supply to reduce production of nitrogen oxide.
The EGR device needs to recirculate high-temperature exhaust gas, and thus has an EGR cooler for cooling the exhaust gas.
Because the existing EGR cooler typically uses an engine coolant, there are limitations in that a separate cooling line is required, and a position where the EGR cooler is mounted needs to be selected in consideration of a head height of the coolant.
Regarding the head of the coolant, in a case in which a height of the coolant at the EGR cooler side is great, bubbles may be produced in the EGR cooler, and as a result, noise problem may occur due to the bubbles at the time of starting an engine, and a coolant path is blocked by the bubbles such that cooling performance may deteriorate.
FIG. 7 is a schematic diagram of a cooling system for a diesel engine having a turbocharger according to the related art.
Referring to the FIG. 7, an inlet duct 900 is connected to one side of an intercooler 140, and an outlet duct 910 is connected to the other side of the intercooler 135.
Intake air passes the inlet duct 900, the intercooler 140, and the outlet duct 910 to be supplied to a combustion chamber of an engine. The intake air is cooled by outside air that passes the intercooler 140. While the intake air is cooled by the outside air, the cooling performance may be deteriorated.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.